1. Field of the Invention
The present invention relates to an improvement in a pneumatically driven bellows pump with a bellows that is reciprocable by a pneumatic force.
2. Discussion of the Background
Conventionally, the pump of the type or a reciprocable pump includes a cylinder 51 and cylinder heads 52 arranged at the opposite ends of the cylinder 51, as illustrated in FIG. 8. Outside of the cylinder 51 are provided a plurality of slide cylinders 53 which interconnect the cylinder heads 52 of the opposite ends of the cylinder 51 together. Interlocking shafts 54 are respectively inserted into the slide cylinders 53, each being secured at its opposite ends to interconnecting plates 55 via mounting bolts 56.
A pair of pistons 57 are oppositely disposed within the cylinder 51, which respectively include pump shafts 59 that are reciprocable along the longitudinal axis of the pump and with regard to shafts 58 extending inwardly from the central portions of the corresponding interconnecting plates 55, and shaft plates 60 mounted to corresponding ends of the pump shafts 59. The pistons 57 are respectively supported by bellows bodies 63 whose outer ends are respectively mounted to corresponding shaft plates 60 via mounting bolts 61, and inner ends are respectively welded to a pump-driving member 62. The pistons 57 are reciprocable along the longitudinal axis of the pump by the expansion and contraction of the bellows bodies 63. An air chamber 64 for allowing the bellows bodies 63 to be reciprocated therein is formed by the cylinder 51, the cylinder heads 52 and the shaft plates 60.
A sensor (not shown) senses the stroke end of the bellows in order to allow the switching of the introduction of the airflow for the air chamber 64. Whereby, fluids or the like can be discharged from the pump-driving member 62 via reciprocation of the pistons 57. Valves 65 are respectively urged by springs 66 so that the oppositely positioned bellows within the pump can be communicated with each other.
In accordance with the pump of the above arrangement, the bellows bodies 63 which limit the reciprocation of the pistons 57 seal the spaces inside of the bellows by the arrangement that the inner ends of the bellows bodies 63 are welded to the pump-driving member 62. Referring to FIG. 9, as an alternative to this arrangement, the bellows bodies 63 whose outer ends of the bellows bodies 63 are respectively mounted to the shaft plates 67 are held at their inner ends between pump-driving member 68 and spacers 69, and fixed therebetween via bolts 70, as illustrated in FIG. 9, in which the arrangement only for one of the bellows bodies 63 are illustrated, since the arrangement for another bellows body 63 is the same as that for the one bellows body 63.
When parts such as the bellows bodies 63 are damaged in the pump of the above arrangement, it may not easy to replace them with new ones since the replacement of these parts involves a troublesome work due to the above arrangement. Thus, the pump having the above arrangement may be in trouble with its maintenance.
To avoid such trouble, it is conceivable to employ the arrangement that the bellows bodies 63 are mounted to the pump-driving member 62 by fastening screws or bolts. However, this arrangement also poses a problem that heat or vibration caused by the operation of the pump may loosen the screws or bolts, and subsequently cause clearances in the mounting portion of the bellows bodies. This may lead to leakage of the fluid, and deteriorate a sealing effect within the bellows bodies 63. Therefore, this arrangement does not provide an essential solution for the above problem.
Therefore, the present invention has been conceived to solve the above problems. It is an object of the present invention to provide a pneumatically driven bellows pump with the arrangement that has ease of maintenance of the pump by replacing the bellows in a simple manner.